Chapter2-CancerINTRODUCTIONNeilPearce,PaoloBoffettaandManolisKogevinasMagnitudeoftheProblemThefirstclear-cutevidenceofcancercausationinvolvedanoccupationalcarcinogen(Checkoway,PearceandCrawford-Brown1989).Pott(1775)identifiedsootasthecauseofscrotalcancerinLondonchimney-sweeps,andgraphicallydescribedtheabysmalworkingconditions,whichinvolvedchildrenclimbingupnarrowchimneysthatwerestillhot.Despitethisevidence,reportsoftheneedtopreventfiresinchimneyswereusedtodelaylegislationonchildlabourinthisindustryuntil1840(Waldron1983).Anexperimentalmodelofsootcarcinogenesiswasfirstdemonstratedinthe1920s(Decoufle1982),150yearsaftertheoriginalepidemiologicalobservation.Insubsequentyears,anumberofotheroccupationalcausesofcancerhavebeendemonstratedthroughepidemiologicalstudies(althoughtheassociationwithcancerhasusuallyfirstbeennotedbyoccupationalphysiciansorbyworkers).Theseincludearsenic,asbestos,benzene,cadmium,chromium,nickelandvinylchloride.Suchoccupationalcarcinogensareveryimportantinpublichealthtermsbecauseofthepotentialforpreventionthroughregulationandimprovementsinindustrialhygienepractices(PearceandMatos1994).Inmostinstances,thesearehazardswhichmarkedlyincreasetherelativeriskofaparticulartypeortypesofcancer.Itispossiblethatotheroccupationalcarcinogensremainundetectedbecausetheyinvolveonlyasmallincreaseinriskorbecausetheysimplyhavenotbeenstudied(DollandPeto1981).Somekeyfactsaboutoccupationalcanceraregivenintable2.1.Table2.1Occupationalcancer:Keyfacts·Some20agentsandmixturesareestablishedoccupationalcarcinogens;asimilarnumberofchemicalsarehighlysuspectedoccupationalcarcinogens.·Inindustrializedcountries,occupationiscausallylinkedto2to8%ofallcancers;amongexposedworkers,however,thisproportionishigher.·Noreliableestimatesareavailableoneithertheburdenofoccupationalcancerortheextentofworkplaceexposuretocarcinogensindevelopingcountries.·Therelativelylowoverallburdenofoccupationalcancerinindustrializedcountriesistheresultofstrictregulationsonseveralknowncarcinogens;exposuretootherknownorhighlysuspectedagents,however,isstillallowed.·Althoughseveraloccupationalcancersarelistedasoccupationaldiseasesinmanycountries,averysmallfractionofcasesisactuallyrecognizedandcompensated.·Occupationalcanceris-toaverylargeextent-apreventabledisease.Occupationalcausesofcancerhavereceivedconsiderableemphasisinepidemiologicalstudiesinthepast.However,therehasbeenmuchcontroversyregardingtheproportionofcancerswhichareattributabletooccupationalexposures,withestimatesrangingfrom4to40%(Higginson1969;HigginsonandMuir1976;WynderandGori1977;HigginsonandMuir1979;DollandPeto1981;HoganandHoel1981;VineisandSimonato1991;AitioandKauppinen1991).Theattributablecancerriskisthetotalcancerexperienceinapopulationthatwouldnothaveoccurrediftheeffectsassociatedwiththeoccupationalexposuresofconcernwereabsent.Itmaybeestimatedfortheexposedpopulation,aswellasforabroaderpopulation.Asummaryofexistingestimatesisshownintable2.2.UniversalapplicationoftheInternationalClassificationofDiseasesiswhatmakessuchtabulationspossible(seebox).TheInternationalClassificationofDiseasesHumandiseasesareclassifiedaccordingtotheInternationalClassificationofDiseases(ICD),asystemthatwasstartedin1893andisregularlyupdatedunderthecoordinationoftheWorldHealthOrganization.TheICDisusedinalmostallcountriesfortaskssuchasdeathcertification,cancerregistrationandhospi...
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